In a power network, such as a transmission and distribution grid, a busbar provides common connection for several electric circuits. A busbar may for instance form part of a substation. Busbar faults, although relatively rare compared to line faults, may cause significant loss and disturbances in the power network.
Intelligent Electronic Devices (IED) are utilized to provide reliable protection against busbar-related short circuits and ground faults. In case a fault occurs on a busbar, all circuits supplying the fault current must trip, i.e. they must be disconnected, in order to isolate the fault.
A multiple busbar arrangement comprises several busbars. A busbar arrangement is often divided into so-called bus zones with each bus zone bounded by circuit breakers to further reduce the impact of busbar faults. A protection zone is a protection area of one or more merged bus zones. Protection zones for a given busbar arrangement may vary and should be dynamically selected.
Efficient dynamic zone selection is a key function for digital busbar protection. Numerical-algorithm-based zone selection ensures accurate yet fast dynamic linking of measurement transformers to appropriate protection zones and selectively determine the circuit breakers to trip in the event of a busbar fault.
U.S. Pat. No. 6,411,865 provides a system for protection zone selection in an electric power system. The system uses graph theory in order to represent a power system bus arrangement in such a way that the protection zones for the bus can be readily changed to accommodate a change of configuration of the bus arrangement.
However, the approach of U.S. Pat. No. 6,411,865 may be quite complex.